1. Field of the Invention
The present invention relates to a semiconductor device and a method of fabricating the semiconductor device, and particularly to a semiconductor device having a double-sided electrode structure and a method of fabricating the semiconductor device.
2. Description of the Related Art
In recent times, the development of three-dimensional package technologies whose packaging density is higher have progressed because of the miniaturization of electronic devices such as mobile telephones. Within three-dimensional package technologies, a method called package-on-package (POP), where another package is laminated on one package, is promising. In POP, a package having a double-sided electrode structure (double-sided electrode package) is used. In a double-sided electrode package, inner wires that are connected to a semiconductor chip, penetrating electrodes that interconnect electrodes on a package surface side and the inner wires, and penetrating electrodes that interconnect electrodes on a package back surface side and the inner wires are necessary.
Conventionally, double-sided electrode packages of various structures have been proposed. For example, in Japanese Patent Application Publication (JP-A) No. 2002-158312, there is described a resin-sealed type double-sided electrode package. In this double-sided electrode package, penetrating electrodes are disposed in a sealing resin layer that seals a semiconductor chip, and electrodes on a surface side and inner wires are interconnected via these penetrating electrodes.
Further, in JP-A No. 2003-249604, there is described a lead frame type double-sided electrode package. In this package, part of an inner lead is exposed to the outside of a resin sealing material, and a surface and a back surface of the inner lead are used as external electrodes. Here, the inner lead plays the role of a penetrating electrode.
Further, in JP-A No. 2005-235824, there is described a ball grid array (BGA) type double-sided electrode package. In this package, stepped portions are disposed in a package substrate, end portions of wire bonding-use electrodes are exposed to these stepped portions, and these end portions and electrodes on a surface side or a back surface side are interconnected by penetrating electrodes that penetrate the package substrate.
In order to package these double-sided electrode packages in high density, it is necessary to thin the individual packages. For example, in JP-A No. 2005-235824, the stepped portions are disposed in the package substrate, and the package substrate is mechanically grinded from the back surface side to thereby thin the package.
However, the structure of a conventional double-sided electrode package is not one where electrodes on the surface side are arranged in an arbitrary layout, and it lacks the flexibility of interconnecting upper and lower packages. Further, the sealing resin layer is formed by transfer, but in transfer, it has been difficult to thinly form the sealing resin layer because molding is performed using a mold.